Process and apparatus for making supported catalyst systems for olefin polymerization

Abstract

A process to support a homogeneous catalyst on a porous solid support is performed in two separate zones. In the first zone the solid is contacted, under stirring, with an amount of a catalyst solution lower than the total pore volume of the solid. In the second zone the solid is dried from the solvent while flowing under pneumatic conveying. A loop circulation of solid is established between the two zones, so that the solid is subject to more contacting steps. The process is particularly suitable to support a metallocene-alumoxane polymerization catalyst on a porous prepolymer. The process can be advantageously performed in continuous, thus fitting the needs of an industrial scale production process.

1. A process for preparing a supported catalyst comprising the steps of:
 (a) preparing a catalyst solution comprising a soluble catalyst component; 
 (b) introducing into a contacting vessel: 
 (i) a porous support material in particle form, and 
 (ii) a volume of the catalyst solution not greater than the total pore volume of the porous support material introduced; 
 (c) discharging the solid material resulting from step (b) from the contacting vessel and introducing it into an evaporation zone where it is suspended in an inert gas flow under such conditions that the solvent evaporates; and 
 (d) reintroducing at least part of the material resulting from step (c) into the contacting vessel together with another volume of the catalyst solution not greater than the total pore volume of the reintroduced material. 
 
     
     
       2. The process according to  claim 1  wherein the material resulting from step (d) is subjected to further cycles of steps (c) and (d). 
     
     
       3. The process according to  claim 1  wherein the contacting vessel is kept under stirring. 
     
     
       4. The process according to  claim 1  wherein the operations are carried out continuously and wherein the porous support material is continuously fed and the solid material resulting from step (b) is continuously discharged at any suitable point where the circulating solid flows, the inert gas is continuously fed at a point subsequent to the point of discharge of the solid material from the contacting vessel, and the inert gas containing solvent is withdrawn from any suitable point. 
     
     
       5. The process according to  claim 1  wherein the volume of the catalyst solution fed into the contacting vessel is from 20 to 80% of the total pore volume of the porous support material fed into the contacting vessel. 
     
     
       6. The process according to  claim 5  wherein the volume of the catalyst solution fed into the contacting vessel is from 50 to 60% of the total pore volume of the porous support material fed into the contacting vessel. 
     
     
       7. The process according to  claim 1  wherein the contacting vessel is a column jacketed for temperature control and provided with a mechanical stirring device. 
     
     
       8. The process according to  claim 1  wherein the evaporation zone is a pipe provided with a jacket for temperature control. 
     
     
       9. The process according to  claim 1  wherein the inert gas is nitrogen. 
     
     
       10. The process according to  claim 1  wherein the contacting vessel is equipped with a screw valve for the withdrawal of the solid material. 
     
     
       11. The process according to  claim 1  wherein the catalyst solution comprises a metallocene compound. 
     
     
       12. The process according to  claim 11  wherein the catalyst solution comprises an aluminium alkyl compound. 
     
     
       13. The process according to  claim 1  wherein the porous support material is a porous polyolefin prepolymer. 
     
     
       14. The process according to  claim 13  wherein the prepolymer has a porosity of at least 0.3 ml/g. 
     
     
       15. The process according to  claim 14  wherein the prepolymer has a porosity of at least 1.5 ml/g. 
     
     
       16. The process according to  claim 11  wherein the solvent of the catalyst solution is an inert hydrocarbon solvent. 
     
     
       17. The process according to  claim 12  which is carried out in a first phase when all the metallocene compound together with part of the aluminium alkyl compound is contacted with the porous support material, and in a second phase when the remaining amount of aluminium alkyl compound is contacted with the porous support material. 
     
     
       18. The process according to  claim 11  wherein two different metallocene compounds are used, the said process being carried out in a first phase when one metallocene is contacted with the porous support material, and in the second phase when the other metallocene is contacted with the porous support material. 
     
     
       19. The process according to  claim 18  wherein an aluminium alkyl compound is contacted with the porous support material, part along with one metallocene in the first phase, part along with the other metallocene in the second phase, and part in a further contacting phase. 
     
     
       20. An apparatus comprising a contacting vessel, equipped with a mechanical stirring device and means for discharging a solid in particle form from the contacting vessel, a line for introducing gas at a point after the discharging means, an evaporation zone, means for introducing a catalyst solution into the contacting vessel, and means for separating the particulate solid from the gas stream. 
     
     
       21. The apparatus according to  claim 20 , wherein the contacting vessel and the evaporation zone are jacketed for temperature control. 
     
     
       22. The apparatus according to  claim 20  wherein a condenser is provided to separate the solvent of the catalyst solution from the gas stream coming from the means for separating the solid from the gas stream. 
     
     
       23. The apparatus according to  claim 20  which is provided with means for continuously introducing the solid into the contacting vessel and for continuously discharging the solid at a point where it has come out from the evaporation zone. 
     
     
       24. The apparatus according to  claim 23  which is provided with a further evaporation zone placed downstream of the point of discharge of the solid.